The present invention relates to a probe for the coagulation of biological tissue.
German patent DE 41 39 029 A1 discloses a probe for the coagulation of biological tissue in which an ionizable inert gas, in particular argon, is delivered by gas-supply means to a gas outflow opening formed at a distal end of the probe, coaxially or in a side wall. In the interior of the probe electrode devices are provided to conduct a coagulation current from a high-frequency source into the gas and through the gas into the biological tissue, which is devitalized by the current or by the heat produced in the ionized gas.
One of the problems associated with the known arrangement is that the plasma current, i.e. the region of ionized gas within the overall gas current, cannot be aimed entirely accurately, and hence the site in the biological tissue through which current flows cannot be precisely delimited. This problem becomes considerable when an operation is to be carried out in a very confined region such as a narrow cavity in the body. One example is the use of plasma coagulation in cases of nasal concha hyperplasia. In such confined spaces there is a risk that the argon plasma beam will unintentionally be applied to healthy tissue or to vulnerable structures such as nerves.
The object of the present invention is to provide a probe of the kind described above that overcomes or substantially mitigates the aforementioned problems and that facilitates its manipulation with increased safety.
According to the present invention there is provided a probe for the coagulation of biological tissue, comprising a probe body defining a gas outflow opening; a gas-supply means to supply an ionizable inert gas or noble gas to the outflow opening; an electrode to conduct a coagulation current from an HF source into the gas and through the latter into the biological tissue; and a protective device comprising a mask which is made of an insulating material and which is so constructed and attachable to the body of the probe that regions of the biological tissue that should not be coagulated can be shielded by the mask.
The shielding that can be achieved by both the direct contact between the mask and the part of the tissue to be protected and also by the insulating material of which the mask is made increases the distance the arc would have to travel to reach the protected tissue. In this way, the arc is directed only to the parts of the tissue closer to the opening or within a shorter distance of travel.
Preferably, the probe body is of an elongated, tubular construction and defines the outflow opening in a side wall thereof. In this case the mask is preferably positioned on the side of the probe opposite the gas outflow opening, so that the gas stream emerging from the side of the probe produces a plasma beam that is only aimed in substantially this direction and that does not, on account of special electrical conditions, for example caused by a particularly low resistance of certain parts of the tissue, suddenly migrate backward, toward the side of the probe opposite the outflow opening.
Preferably also, at least the mask of the protective device is made from a flexibly deformable material. In addition, the mask is advantageously from an elastically deformable material. This makes it possible for the protective device or the mask to be brought into contact with the part of the tissue that is not to be coagulated with no fear of mechanical injury. Given an appropriate construction of the protective device, namely such that it projects beyond the distal end of the probe, it can be ensured that the protective device as a whole can be used to prevent mechanical injury to tissue by the probe.
Preferably also, the protective device is detachably fastened to the body of the probe. The device can then be sterilized before each re-use or be constructed as a disposable component manufactured by injection molding.
Preferably also, the mask defines a spade- or spoon-shape with an uninterrupted surface. Advantageously the mask projects forward beyond the end region of the probe as well as outward on both sides, to ensure a secure and simple masking of parts of the tissue that should not be coagulated.
Preferably also, the mask is made of a transparent material in order that a user can see clearly the area below the mask, which further simplifies manipulation of the probe.
An embodiment of the invention will now be described by way of example with reference to the accompanying drawings.